<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // 需求：用户可以选择存钱、取钱、查看余额和退出功能
        let money = 100
        while (true) {
            let re = +prompt(`
            请选择操作：
            1.存钱
            2.取钱
            3.查看余额
            4.退出
            `)
            if (re === 4) {
                break
            }
            switch (re) {
                case 1:
                    let cun = +prompt('请输入存款金额：')
                    money = money + cun
                    break
                case 2:
                    let qu = +prompt('请输入取款金额：')
                    money = money - qu
                    break
                case 3:
                    alert(`您的银行卡余额是${money}`)
                    break 
            }
        }
    </script>
</body>
</html>